As everyone knows, a recording medium comprises two surfaces. In one situation, the two surfaces are identical, without any differences; and in the other situation, the two surfaces are not identical, such as a thermal sensitive paper, one surface of which has a thermal sensitive coating while the other surface of which has no coating, and a magnetic ticket, one surface of which has a magnetic stripe while the other surface of which has no magnetic stripe. To describe conveniently, a recording medium with two surfaces which are not identical is named as a recording medium with front and back surfaces, wherein the front surface is called as a surface to be processed while the back surface is called as a non-processing surface.
For a traditional recording medium processing apparatus such as a printing apparatus and a magnetic head apparatus, a printing head or a magnetic head is located at one side of a channel, therefore it is necessary for the front surface (i.e., the printing surface or the magnetic surface) of the recording medium to correspond with the printing head or the magnetic head. However, operation errors made by the operator often result in a non-correspondence between the front surface of the recording medium and the printing head or the magnetic head, and the printing of the recording medium or the processing of magnetic reading/writing cannot be accomplished smoothly. To solve this problem, a recording medium overturning mechanism is provided in a Japanese Patent Publication No. 06-271166, as shown in FIGS. 1a, 1b and 1c. The recording medium overturning mechanism comprises a first channel 10, a second channel 20, a rotating roller 80, a switching member 81 and an electromagnet 82. The switching member 81 is located between the first channel 10 and the second channel 20 for switching the travelling direction of the recording medium. The electromagnet 82 is provided to control whether the second channel 20 is able to convey a medium or not. FIG. 1a is a conveying path of the recording medium when it is not overturned. The switching member 81 rotates in the direction D to make the recording medium 2 enter the first channel 10 via an entry A and exit through an exit B. FIGS. 1b and 1c show a conveying path of the recording medium when it is overturned. The specific method comprises: step a), in which the switching member 81 rotates in the direction F to make the recording medium 2 enter the second channel 20 via the entry A, the electromagnet 82 drives a driving roller 77 to cooperate with a driven roller 75 of the second channel 20, and the medium is driven to enter the second channel 20; and step b), in which the electromagnet 82 drives the driving roller 77 to separate from the driven roller 75 of the second channel 20, meanwhile a floating wheel 74 is driven to cooperate with the rotating roller 80, and the medium is conveyed into the second channel 20 in a direction opposite to the direction of step a) and exits through the exit B.
At least the following problems are present in the prior art: the existing recording medium overturning mechanism comprises a first channel, a second channel, a switching member, an electromagnet, a rotating roller and other parts, the first channel and the second channel further comprise multiple belts and several rotating rollers, thus making the structure complex; meanwhile, when the recording medium is overturned, the switching member, the driving roller and the floating wheel of the second channel need to be switched, respectively, thus making the control intricate.